At least three women suicide bombers blew themselves up on the outskirts of Maiduguri, Nigeria, killing at least four people and themselves.

The explosions at dawn Friday were carried just hours after two suicide attacks inside a mosque also in Maiduguri, the capital of northeastern Borno state killed 37 people, according to a VOA reporter at the scene.

Survivor Sherif Amadu told VOA from his hospital bed that the two bombs exploded at an interval of a few minutes. The first was inside the mosque and the second outside. Amadu was one of dozens wounded in the attack.

Nigerian national emergency officials say the blasts in the mosques were timed so that the second one killed many people who had gathered to offer help after the first blast.

The bombs were detonated while people were gathered for evening prayers. Boko Haram militant group is suspected for the wave of suicide attacks in northeastern region of the country.

While no one has claimed responsibility for the blasts, the Boko Haram Islamic extremists have announced their intention to create a strict Islamic state there.

Boko Haram has staged cross-border attacks in the other nations bordering the region.

Agence France Presse is reporting that the U.S. will conduct surveillance and intelligence operations against Boko Haram inside Nigeria.

AFP says the operations will be part of the deployment announced by President Barack Obama earlier this week. Obama announced that the U.S. is sending U.S. military personnel to conduct airborne surveillance of militant activity in an effort to help Nigeria, Chad, Cameroon, Benin and Niger in their joint initiative to wipe out the militant threat.

Obama says the U.S. force will be headquartered in Cameroon and will eventually number about 300. A U.S. defense official has said they will stay "as long as their presence is requested.

Rights group Amnesty International said this month that Boko Haram has killed at least 1,600 civilians since the start of June, and more than 3,500 civilians overall during 2015.

The group has been fighting to establish a strict Islamic caliphate in northern Nigeria since 2009.